Following his father's death, his mother became regent for the new king Afonso VI, Peter's elder, partially paralyzed, and mentally unstable brother.

[4] In January 1668, shortly before Spanish recognition of Portugal's restoration of independence, Peter acquired political ascendancy over his brother and was appointed regent,[5][6] banishing Afonso to the Azores[1] and, later, Sintra where he died in 1683.

After his coup in 1667, Peter restored the nobility to their full power[13] and government by councils of nobles reached a high point during his reign[14] because he required their support in deposing Alfonso VI.

Isabel Luísa was proclaimed heir presumptive to the throne at the Portuguese Cortes of 1674,[16] Peter promulgating a letter on the regencies and tutorships of Kings to better found the rights of his daughter.

In 1674 his main concern was to improve the defenses of the realm, asking for contributions from the Junta dos Três Estados to the keeping of border garrisons, its paraphernalia and indispensable works in castles and forts.

Veríssimo Serrão, in his book "History of Portugal", Volume V, page 213 says the following, "The shipments from India and Brazil were the main object of greed so that the Crown was obliged to arm a fleet of 11 boats.

But it would all turn ineffective to the extent that the embassy of the Duke of Cadaval, sent to Turin in May 1682, did not reach or did not finish the project,[20][19] by pressures, perhaps, of Louis XIV on the dynasty of Savoy.

[21] In the court there was a strong French party, headed by the Duke of Cadaval, the then Count of Vila Maior and by the Viscount of Ponte de Lima, but others favored a closer alliance with Spain.

The King fixed the basis of his Brazilian policy in two main points: the importation of precious metals and stones and the expansion of the borders of the colony to the banks of the Río de la Plata.

The reputation of the Paulistas was such that, urged by Barbacena, Peter wrote to twelve frontiersmen Piratinganos, and provided them with the "incomparable honor" of a direct summoning them to place their employment at the royal service.

The King ceded his seigniorage rights, tribute owed to him, in favor of the better functioning of this institution, that minted the first Brazilian coins for usage within the colony.

By the end of Peter's reign, there were two big problems in Brazil: the dispute over the Colónia do Sacramento that, even though since 1680 recognized as Portuguese territory, was occupied by the Spanish in 1705, and the first conflicts between Paulistas and Emboabas, competing outsiders, including metropolitan people (ie.

It was during his time that the Palace of Salvaterra de Magos became again the favorite place of court, Pedro II settling there in the months of January and February, to devote himself to the sport of riding.

(...) Master of a great memory, the monarch never refused an audience to whoever asked it, was it day or night, delighted to listen to others and to discuss the issues in the smallest details.